19 November 2013

Vaccines may someday prevent heart attacks

People routinely get vaccinations to ward off the flu – could there be a vaccine in the future that would prevent a heart attack?

People routinely get
vaccinations to ward off the flu or prevent infectious diseases such as measles
and whooping cough. Could there be a vaccine in the future that would prevent a
heart attack?

Two animal studies suggest
that vaccines might someday be used to reduce high cholesterol levels and lower
blood pressure, according to findings presented Monday at the American Heart
Association (AHA) annual meeting in Dallas.

In both cases, the vaccines
interrupt processes in the body that, if left alone, can lead to high
cholesterol and elevated blood pressure.

The first study, out of
Vienna, found that mice and rats had lower cholesterol levels for a year
following treatment with a vaccine that protects a cell's ability to remove
"bad" LDL cholesterol from the bloodstream.

Lowering cholesterol

"This is one of the
most exciting things that's now under development in the controllability of
cholesterol," said Dr James Howard, an AHA spokesperson and an
endocrinologist and internist at MedStar Washington Hospital Centre in Washington,
DC.

The vaccine targets an
enzyme called PCSK9. This enzyme causes cells to become less able to yank LDL
cholesterol from the bloodstream and convert it into hormones or other useful
products, Howard said.

"When you make an
antibody to it, it just can't function," he said of PCSK9.

By reducing the amount of
active PCSK9 in a body, the vaccine also reduces the cholesterol levels as
cells become more efficient in using cholesterol.

"It has incredible
power to lower LDL cholesterol, and can be taken with statins," Howard
said.

Scientists note that
research conducted in animals often fails to provide similar results in humans.

The second study, this one
from Japan, used a different vaccine to lower high blood pressure in laboratory
rats for up to six months.

Sodium balance regulation

This vaccine interferes
with a hormone called angiotensin II, which increases blood pressure by causing
blood vessels to constrict. Medications already are widely used to block
angiotensin II and control blood pressure, but they have to be taken daily to
be effective.

"It's a hormone that
increases blood pressure, and many of the common drugs antagonize it and reduce
blood pressure," said Barbara Howard, a senior scientist at MedStar Health
Research Institute and a professor at Georgetown University Hospital, in
Washington, DC. "The idea is if you can knock out the production, you can
have a sustained reduction that will last longer."

There are some concerns
about medicines or vaccines that target this hormone, however. "It's part
of a very complex network of hormones that regulate sodium balance in your
body," she said. "It has to be very tightly regulated, or it can
cause damage to the whole vascular system."

In this study, the vaccine
reduced the rats' blood pressure for months and reduced damage to the heart and
blood vessels associated with high blood pressure. It also did not cause any
damage to the kidneys, heart or liver.

Human trials

While these findings are
promising, Howard said there needs to be more study before it is ready as a
vaccine for humans.

"There's a lot of
danger of overshooting and disturbing that sodium balance, and they didn't give
any real data in this report," she said. "It's got to be done in
humans, and it's got to be accompanied by many more measures of functional
safety. If you lower it enough to affect blood pressure, can you do that
without affecting sodium balance?"

At this point, the vaccine
is at least five to six years away from human trials, according to study
co-author Dr Hiroshi Koriyama of Osaka University, in Japan.

There likely will be a
similar amount of time needed to bring the cholesterol vaccine to human trials,
said AHA spokesperson Dr James Howard.

However, he noted that
human trials now are taking place for another form of the cholesterol vaccine
that has to be taken every couple of weeks by injection.

In the meantime, the AHA
recommends eating a heart-healthy diet, getting weekly aerobic and
muscle-strengthening activity, and avoiding tobacco smoke as good ways to help
control cholesterol.

Because the studies were
presented at a medical meeting, the data and conclusions should be viewed as
preliminary until published in a peer-reviewed journal.

More information

For more information on
treatment of high cholesterol, visit the American Heart Association.

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